/*
 * Copyright (C) 2007 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.io;

import java.io.Closeable;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.annotation.Nullable;

/**
 * Utility methods for working with {@link Closeable} objects.
 * 
 * @author Michael Lancaster
 * @since 2009.09.15 <b>tentative</b>
 */
public final class Closeables {
    private static final Logger logger = Logger.getLogger(Closeables.class
            .getName());

    private Closeables() {
    }

    /**
     * Closes a {@link Closeable}, with control over whether an
     * {@code IOException} may be thrown. This is primarily useful in a finally
     * block, where a thrown exception needs to be logged but not propagated
     * (otherwise the original exception will be lost).
     * 
     * <p>
     * If {@code swallowIOException} is true then we never throw
     * {@code IOException} but merely log it.
     * 
     * <p>
     * Example:
     * 
     * <p>
     * 
     * <pre>
     * public void useStreamNicely() throws IOException {
     * SomeStream stream = new SomeStream("foo");
     * boolean threw = true;
     * try {
     *   // Some code which does something with the Stream. May throw a
     *   // Throwable.
     *   threw = false; // No throwable thrown.
     * } finally {
     *   // Close the stream.
     *   // If an exception occurs, only rethrow it if (threw==false).
     *   Closeables.close(stream, threw);
     * }
     * </pre>
     * 
     * @param closeable
     *            the {@code Closeable} object to be closed, or null, in which
     *            case this method does nothing
     * @param swallowIOException
     *            if true, don't propagate IO exceptions thrown by the
     *            {@code close} methods
     * @throws IOException
     *             if {@code swallowIOException} is false and {@code close}
     *             throws an {@code IOException}.
     */
    public static void close(@Nullable Closeable closeable,
            boolean swallowIOException) throws IOException {
        if (closeable == null) {
            return;
        }
        try {
            closeable.close();
        } catch (IOException e) {
            if (swallowIOException) {
                logger.log(Level.WARNING,
                        "IOException thrown while closing Closeable.", e);
            } else {
                throw e;
            }
        }
    }

    /**
     * Equivalent to calling {@code close(closeable, true)}, but with no
     * IOException in the signature.
     * 
     * @param closeable
     *            the {@code Closeable} object to be closed, or null, in which
     *            case this method does nothing
     */
    public static void closeQuietly(@Nullable Closeable closeable) {
        try {
            close(closeable, true);
        } catch (IOException e) {
            logger.log(Level.SEVERE,
                    "IOException should not have been thrown.", e);
        }
    }
}
